Instrumented indentation test is a promising non-destructive method to determine mechanical properties. This paper proposes a new approach to determine the plastic properties of bulk metal materials (including yield stress, strain-hardening exponent (n) and strain-hardening rate (K)), which couples an experimental load-displacement curve with finite element method. The load–displacement curve was obtained from continuous instrumented indentation test. Then a hybrid particle swarm optimization was employed to minimize the deviation between experimental and simulated load-displacement curves. As a combination of particle swarm optimization and simulated annealing, the simulated annealing particle swarm optimization is an economical and effective algorithm to identify plastic parameters. It was observed that the maximum error of strain-hardening rate extracted from the macro indentation test was 8.2 percent contrast to that determined by the conventional tensile test, and the maximum error of strain-hardening exponent was 4.7% respectively.